add param for csit-hc2vpp-verify for release testing

add param for csit-hc2vpp-verify for release testing

To be able to test released packages we need to add
new parameter to csit-hc2vpp-verify-func job.

Usage: In commit message for release branch add "honeycomb" parameter
with desired version after trigger keyword.
Example: verify-hc2vpp-func honeycomb=19.04-release

To test regular RC versions use trigger keyword
without "honeycomb" param.
Example: verify-hc2vpp-func

Change-Id: I67c9a856e031bb2cec6b18312d86c2fcd342d2ee
Signed-off-by: Michal Cmarada <mcmarada@cisco.com>